Studies on the distribution and mobility of binding sites on the surface of platelet plasma membrane by means of ferritin-conjugated wheat germ agglutinin

HOSHIKAWA Nariyoshi, IMURA Joji, YOTSUMOTO Shoichi, KAWAGUCHI Yukihiro, SHIRASAWA Kenjiro

doi:10.2491/jjsth1970.14.270

The distribution and mobility of binding sites on the plasma membrane of platelets were studied by using ferritin-conjugated wheat germ agglutinin (F-WGA). Washed human platelets were incubated with F-WGA (final ferritin concentration: 0.1mg/ml) at 37°C after or before glutaraldehyde fix atio at room temperature. In incubation with F-WGA after fixation, the plasma membrane of disk shaped, nonactivated platelets was diffusely studded with the particles. The binding sites of F-WGA were remarkably decreased in number with pretreatment of neuraminidase (f. c. 10 or 20IU/ml) after fixation. When platelets were incubated with F-WGA and followed by fixation, the binding sites on the cell surface became loose and irregular in arrangement showing lateral migration. With the lapse of time, the particles were taken up into the dilated open canalicular system. After further incubation with phosphate buffered saline, such a distribution became looser and the particles increased in number in the open canalicular system. When platelets were reincubated with F-WGA and fixed after washing, the particles were distributed again on surface of activated platelets. The native ferritin used in the respective control experiment was never bound on the membrane of platelets. These findings suggest that WGA generally binds to N-acetylneuraminic acid (sialic acid) of the cell surface. The results are absolutely compatible with those of the mobility of anionic sites on the cell membrane obtained by utilization of cationized ferritin. In conclusion, the diffuse distribution of sialic acid may contribute to the unstickness of platelets in association with anionic charge on the cell surface. Under circumstance, however, mobility of binding sites may facilitate activation of platelets due to some kinds of stimulation.

Studies on the distribution and mobility of binding sites on the surface of platelet plasma membrane by means of ferritin-conjugated wheat germ agglutinin

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